Conventional complementary metal-oxide semiconductor (CMOS) image sensors include pixel arrays that collect electric charge during exposure times (also referred to as exposure periods).
In some conventional CMOS image sensors, the pixel array is controlled by a single exposure time, which applies to the entire pixel array. In more advanced image sensors with wide dynamic range (WDR), the pixel array exposure time for the pixel array may be controlled according to a given pattern of exposure times.
FIG. 9 illustrates a WDR example in which a single long exposure time and a single short exposure time are applied to the pixel array alternately on a line-by-line basis. In this example, the exposure duration is changed from long to short and vice versa every two lines.
FIG. 10 illustrates another WDR example in which the long and short exposure times are applied in a mosaic pattern where each group of four pixels (referred to as a “quad pixel”) changes from long to short and vice versa.
Each of the conventional approaches for controlling exposure of pixel arrays, however, forces image processing to set the proper long and short exposure time for the entire array, even though certain areas of the array may require different exposure times for increasing dynamic range depending on the scene being captured.